Electrostatic recording apparatus

ABSTRACT

An electrostatic recording apparatus wherein a corona source including a plurality of equidistant conductors are selectively pulsed to generate a corona stream in a space between a backing electrode and the pulsed conductor, this space being defined by an aperture in a dielectric member which moves the aperture in a direction substantially parallel to said conductors.

United States Patent 1111 3,599,225

lmentnr William Babaoff 3.362.325 1/1968 Foster 346/74 X Rochester. NY. 3,413,654 11/1968 Strong..... 346/74 {Ill Appl N'r- 686,238 3,321,768 5/1967 Byrd 1 t 4 346/74 112] Filed NOLZ8, 196 3.3'2|.768 5/l967 Byrd. 346/74 ES 1-15] Patented Aug. 10.1971 OTHER REFERENCES Asslgnce Xemx(orpomuon Xerography: Dessaner S Clark; The Focal Press; 1965;

Rochester, NY.

Pages 20 l -202.

Primary Examiner- Bernard Konick 1541 ELECTROSTATIC RECORDING APPARATUS ASS/Fm"; E 1 G M HQffman 6 Claims. 5 Drawing g Ar1urneysRonald Zibelli. James J. Ralabate and Norman E. 52 vs. Cl. 346/74 125, Schrade l01/DlG.l3,178/6.6A l ll lnt. v M 60111 15/06, v

Gold 15/20 ABSTRACT: An electrostatic recording apparatus wherein a {SUI Field of Search 346/74 ES; corona source including a plurality of equidistant conductors 178/66 A are selectively pulsed to generate a corona stream in a space References (mm between a backing electrode and the pulsed conductor, this space being defined by an aperture in a dielectric member UNITED STATES PATENTS which moves the aperture in a direction substantially parallel L.893.8l0 7/1959 Miller et all r 346/74 to said conductors.

PATENTED AUG I 0 I9?! BUFFER DECODER 5 RE C ORDER ,4 JWIHH B |L CHARACTER CORE MA TR/X FIG. 4

F am

INVEN' FOR. WILL iAM BABAOFF FIG. 5

A 7' TORNEYS ELECTROSTATIC RECORDING APPARATUS This invention relates generally to electrostatic recording, and, more specifically, to recording apparatus employing corona generation.

There exists in the prior art an electrostatic recording process which may be referred to as corona stencil. With this technique a cloud or stream of corona or ions is selectively produced and directed toward a suitable dielectric recording medium. This recording medium has adjacent to its side remote from the corona source a backing electrode biased to attract ions of a particular polarity. Intermediate the recording medium and the corona source there is positioned a conductive stencil or mask which bears character-shaped apertures. The corona stream in passing through one of these apertures toward the recording medium has its cross section so configured so as to correspond to the character represented by the particular aperture. The attracted ions in this shaped corona stream deposit onto the surface of the recording medium thereby constituting a latent electrostatic charge pattern which may be rendered visible and permanent by conventional xerographic development and fixing processes.

The stencil so employed may take various forms such as an endless belt, a rotating drum or disc. However, once the character font or nature of the symbols for the apertures thereof to represent are chosen, only those symbols or characters may be used in any recording. If different fonts or symbols are desired, then a new stencil must be made and incorporated into the system. l I

Therefore, it is an'object of the present invention to improve electrostatic recording utilizing corona generation.

It is also an object of the present invention to improve electrostatic recording wherein any character fonts or symbols may be used without delay or extensive modification.

A still further object of the present invention is to provide an improved electrostatic recording apparatus which is simple and compact.

These and other objects which may become apparent are accomplished in accordance with the principles of the present invention whereina corona source including a plurality of equidistant conductors are selectively pulsed to generate a corona stream in a space between a backingelectrode andthe pulsed conductor, thisspace being defined by an aperture in a dielectric member which moves the aperture in a direction substantially parallel to said conductors.

For a better understanding of the present invention as well as other objects and features thereof, reference may be made to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of the electrostatic recording apparatus in accordance with the principles of the present invention;

FIG. 2 represents a cross-sectional view of the recording station of the present invention;

FIG. 3 illustrates the manner in which alphanumeric information is recorded'in accordance with-the principles of the present invention;

FIG. 4 shows schematically in blockform a typical circuit which may be used with the present invention; and,

FIGS. 5 A-G illustrate typical pulse waveforms generated by the circuit of FIG. 4.

Reference will now be made to FIGS. 1 and 2 which best illustrate the apparatus of thepresent invention.-As shown, a dielectric web 2 may be guided through a recording station via two idler rollers 4 in a direction indicated by the arrow. Generally, this web 2 may be under tension and may be moved in a step-by-step manner by any one. of several conventional means, for example, a motor-indexing clutch combination. For purposes of this description, it is only necessary that such a combination maintain the web motionless during a recording cycle and index this web a predetermined distance between recording cycles. This indexing may be initiated strictly on a 2 timing basis, i.e., the web is indexed afier'every period r where t is slightly longer than the time required to complete a'r'araing cycle. 7

While not a part per se of the present invention, it may be noted that the web 2 may be threaded through conventional xerographic developing and fusing stations, which, for simplicity, are not illustrated in FIG. 1. I

The dielectric web 2 may be in contact with a backing electrode 6 which forms one boundary of a corona space at the recording station. The other boundary of this corona space is formed by a plurality of pulsed electrodes 8 which are substantially parallel with each other in a single plane. As shown, these pulsed electrodes 8 are embedded in the surface of' an insulating block 10 thereby permitting a portion of the insulating block 10 to insulate adjacent electrodes from each other.

Electrodes 8 are referred to as pulsed electrodes to distinguish them for purposes of explanation from electrode 6. Generally, as will be further described hereinafter, voltage pulses may be selectively applied to desired electrodes 8 while backing electrode 6 may be maintained at a constant predetermined reference voltage.

The dielectric constant of the material constituting insulating block l0-is of such a suitable value so as to effectively eliminate any discharge between adjacent electrodes 8.

Further defining the corona space at the recording station is a dielectric mask shown in the form of an endless belt 12 driven via pulleys 14 (in a direction as indicated by the arrows) by motive force provided by motor 16;. This motor is mechanically coupled to pulley by way of a drive belt I8 and shaft 20. This motor has the characteristic of being capable of driving the belt 12 at a substantially constant speed. The actual corona space is defined by any one of a plurality of slits 22 in this belt 12 which is between the pulsed electrodes and the backing electrode. This slit is preferably uniform in width and height and may be rectangularly configured so that its longest dimension is slightly longer than the dimension of the insulating block I0 which lies in the plane of electrodes 8 and transverse thereto. The minimum length which this dimension may have is one equal to the distance sgparating the nonadjacent outermost edges of the two most remote electrodes 8.

Similarly, the dimensions of the backing electrode should preferably be equal to that of the ,pulsedelectrode combination so as to insure a uniform corona spacealongbothdimensions of the recording station.

As shownin FIG. 2, the dielectric belt .12 may move in a contacting relation withth e pulsed electrode array permitting an air gap between it and the dielectric web 2..It should beappreciated that since the belt 12 is a dielectricit will notshort the pulsed electrodes 8.

Referring now to FIG. 4, the recording apparatus as shown in FIG. 1 isrepresented by block 26 andhas a pluralityof inputs 28, such as seven, from a similar plurality ofconventional amplifiers designated by reference numeral 30. As shown in FIG. 2, each one. ofthese inputs 28 is associated-withandcoupled to one of the pulsed electrodes. '1 I V The amplifiers serve to amplify pulses generated ,on the sense lines ofa conventional character magnetic corematrix 32. The character wires of the matrix arein turncoupledto the outputs of a conventional decoder circuit 34 whichacts to decode character codes, for example,stored in an input buffer 36 also of conventional design. A typicalexampleof a decoder and core matrix is shown and described in U. S. Pat. No. 3,012,839. This typical circuit as shownin .FIG. 4 will,,in.the case of character E," generate a plurality of parallel voltage pulse trains as shownin FIGS.;5 A -GJn orderto facilitate this description, the time abscissa for thesepulsetrains runs from right to left as.FIG.-5 is viewed and corresponds with the sequential movement of slit .22 ,dep'icted in ;..FIG. ;3.in .a direction as indicated by the arrow. Thepgsitionof the slit 2j2 as shown inFIG. 3.is such in time that apulse .ispresentat every input 28 to;the recorder 26 thereby creating acorona generating field-between each of the. pulsed electrodes} and backing electrode6. However, due to the interposition of'the dielectric belt 12 in this field, corona is actually generated only along a straight line which is substantially perpendicular to the plane of the pulsed electrodes 28 and which connects the pulsed electrode 8 and the backing electrode. This straight line also must pass through the slit 22 in the recording station since it is only in this area that the field so generated is strong enough to result in corona generation.

As the first pulses in time reach the electrodes 8 the corona streams generated act to deposit charges of one polarity onto the surface of the dielectric web 2 in a configuration which reflects the point or points of intersection of the slit 22 and one or more of the electrodes 8 which is at that time at the proper voltage.

Immediately thereafter, when the slit 22 in FIG. 3 has moved slightly to the left, the second pulses in pulse trains of FIGS. 5-A, 5-D, and 5-G will reach their respective electrodes 8 in parallel to deposit another set of charges on the dielectric web 2. This set of charges will result from corona emitted at the electrode areas 3 by the dashed rectangles designated by reference numeral 38.

This selective corona generation is continued until the entire letter B is recorded on the dielectric web 2 as a latent electrostatic charge pattern. Then another character may be processed and recorded in a similar manner as described.

Obviously the speed at which the slit 22 moves is correlated and synchronized with the reading out of the selected character from the core matrix in any conventional manner.

For expediency, the mask or belt 12 may have as many slits therein as desired so long as the distance separating adjacent slits is slightly greater or equal to the dimension of the recording area or zone on dielectric web 2 which is in the direction of movement ofthe slit 22.

While intended to be in no way limiting the following paranfeters have been used in successful experiments with the present invention:

Slit Width: 5 mils.

Slit Height= one-eighth inch Backing Electrode Voltage l 300 volts Pulsed Electrode Voltage =+700 volts Belt Thickness (Mylar) 4.5 mils Pulsed Electrode Width 0.000] inch Pulsed Electrode Length 6 inches Pulse Electrode Separation 0.0 l 6 inch Pulse Duration 120 microseconds It should be observed that these parameters are functionally interrelated and may beselctively varied as desired for suc- 'cessfultrecording.

While the invention has been described with reference to the embodiment disclosed herein, it is not confined to the details set forth since it is apparent that certain equivalents may be substituted for the components of the preferred embodiment without departing from the scope of this invention. Thus, for example, while the electrodes 8 have been disclosed as being pulsed while the backing electrode 6 is at a reference voltage, the reverse situation may be used wherein the backing electrode is pulsed and selective ones of the electrodes 8 are switched to a reference voltage in response to character signals.

Also, other types of pulse generating circuits may be used to selectively pulse the recorder.

Furthermore, it should be apparent that the belt 12 does not necessarily have to contact the pulsed electrodes 8 nor be separated by a gap from the dielectric recording web 2.

Therefore, it is intended that this invention cover such modifications or changes as may come within the scope of the invention as defined by the following claims:

Iclaim:

1. Recording apparatus comprising:

a. a plurality of linear electrodes lying substantially in a common plane, adjacent ones of said electrodes being substantially equidistant from each other, each of said electrodes having a first and a second end, the proximity between the first end of any one of said electrodes and the first end of an ad acent electrode being greater than the proximity between the second end of said any one of said electrodes and the first end of said adjacent one of said electrodes;

b. a backing electrode having a surface spaced from and substantially parallel to said common plane;

c. selectively movable means having at least one aperture therein movable intermediate said surface and said common plane, said aperture having at least two substantially parallel opposite sides; and,

d. motive means mechanically coupled to said movable means for moving said aperture in a direction from said first ends to said second ends.

2. Recording apparatus as defined in claim 1 further including circuit means for selectively establishing a corona generating field between selected linear electrodes and said backing electrode through said aperture in response to electrical signals.

3 Recording apparatus as defined in claim 1 wherein said selectively movable means includes:

a. an endless belt having said aperture therein; and,

motive means mechanically coupled to said belt for moving said aperture in a direction parallel to the end-to-end dimension of said electrodes and between said surface and said common plane; and

b. said two opposite sides of said aperture being transverse to the direction of movement of said aperture.

4. Recording apparatus as defined in claim I, wherein said movable means includes an endless belt of dielectric material which contacts said linear electrodes and further including means for selectively positioning a recording medium intermediate said surface of said backing electrode and said endless belt.

5. An electrostatic recording system comprising:

a. a plurality of substantially parallel linear electrodes lying in a common plane, each of said electrodes having a first and a second end, the proximity between the first end of any one of said electrodes and the first end of an adjacent electrode being greater than the proximity between the second end of said any one of said electrodes and the first end of said adjacent one of said electrodes;

b. a backing electrode having a surface substantially parallel to said common plane and spaced therefrom;

c. source of reference voltage coupled to said backing electrode;

d. an endless belt having an aperture therein, said aperture having two opposite substantially parallel sides;

e. motive means mechanically coupled to said belt for moving said aperture between said surface and said common plane where the direction of movement is substantially perpendicular to said two opposite sides; and,

f. signal means coupled to said linear electrodes for generating a corona stream through said aperture during movement thereof and between said surface and selected linear electrodes.

6. Apparatus as defined in claim 5 wherein said endless belt is a dielectric material. 

2. Recording apparatus as defined in claim 1 further including circuit means for selectively establishing a corona generating field between selected linear electrodes and said backing electrode through said aperture in response to electrical signals. 3 Recording apparatus as defined in claim 1 wherein said selectively movable means includes: a. an endless belt having said aperture therein; and, motive means mechanically coupled to said belt for moving said aperture in a direction parallel to the end-to-end dimension of said electrodes and between said surface and said common plane; and b. said two opposite sides of said aperture being transverse to the direction of movement of said aperture.
 4. Recording apparatus as defined in claim 1, wherein said movable means includes an endless belt of dielectric material which contacts said linear electrodes and further including means for selectively positioning a recording medium intermediate said surface of said backing electrode and said endless belt.
 5. An electrostatic recording system comprising: a. a plurality of substantially parallel linear electrodes lying in a common plane, each of said electrodes having a first and a second end, the proximity between the first end of any one of said electrodes and the first end of an adjacent electrode being greater than the proximity between the second end of said any one of said electrodes and the first end of said adjacent one of said electrodes; b. a backing electrode having a surface substantially parallel to said common plane and spaced therefrom; c. source of reference voltage coupled to said backing electrode; d. an endless belt having an aperture therein, said aperture having two opposite substantially parallel sides; e. motive means mechanically coupled to said belt for moving said aperture between said surface and said common plane where the direction of movement is substantially perpendicUlar to said two opposite sides; and, f. signal means coupled to said linear electrodes for generating a corona stream through said aperture during movement thereof and between said surface and selected linear electrodes.
 6. Apparatus as defined in claim 5 wherein said endless belt is a dielectric material.
 2. Recording apparatus as defined in claim 1 further including circuit means for selectively establishing a corona generating field between selected linear electrodes and said backing electrode through said aperture in response to electrical signals. 3 Recording apparatus as defined in claim 1 wherein said selectively movable means includes: a. an endless belt having said aperture therein; and, motive means mechanically coupled to said belt for moving said aperture in a direction parallel to the end-to-end dimension of said electrodes and between said surface and said common plane; and b. said two opposite sides of said aperture being transverse to the direction of movement of said aperture.
 4. Recording apparatus as defined in claim 1, wherein said movable means includes an endless belt of dielectric material which contacts said linear electrodes and further including means for selectively positioning a recording medium intermediate said surface of said backing electrode and said endless belt.
 5. An electrostatic recording system comprising: a. a plurality of substantially parallel linear electrodes lying in a common plane, each of said electrodes having a first and a second end, the proximity between the first end of any one of said electrodes and the first end of an adjacent electrode being greater than the proximity between the second end of said any one of said electrodes and the first end of said adjacent one of said electrodes; b. a backing electrode having a surface substantially parallel to said common plane and spaced therefrom; c. source of reference voltage coupled to said backing electrode; d. an endless belt having an aperture therein, said aperture having two opposite substantially parallel sides; e. motive means mechanically coupled to said belt for moving said aperture between said surface and said common plane where the direction of movement is substantially perpendicUlar to said two opposite sides; and, f. signal means coupled to said linear electrodes for generating a corona stream through said aperture during movement thereof and between said surface and selected linear electrodes.
 6. Apparatus as defined in claim 5 wherein said endless belt is a dielectric material. 